As in Mathematicks, so in Natural Philosophy, the Investigation of difficult Things by the Method of Analysis, ought ever to precede the Method of Composition. This Analysis consists in making Experiments and Observations, and in drawing general Conclusions from them by Induction, and admitting of no Objections against the Conclusions, but such as are taken from Experiments, or other certain Truths. For Hypotheses are not to be regarded in experimental Philosophy.

Philosophy is such an impertinently litigious lady that a man had as good be engaged in lawsuits as have to do with her.

Impressed force is the action exerted on a body to change its state either of resting or of moving uniformly straight forward.

I have been much amused at ye singular phenomena resulting from bringing of a needle into contact with a piece of amber or resin fricated on silke clothe. Ye flame putteth me in mind of sheet lightning on a small-how very small-scale.

Physics, beware of metaphysics.

You ask me how, with so much study, I manage to retene my health. Morpheus is my last companion; without 8 or 9 hours of him yr correspondent is not worth one scavenger's peruke. My practices did at ye first hurt my stomach, but now I eat heartily enou' as y' will see when I come down beside you.

Ax: 100 Every thing doth naturally persevere in yt state in wch it is unlesse it bee interrupted by some externall cause, hence... [a] body once moved will always keepe ye same celerity, quantity & determination of its motion.